Pete, On Wednesday, August 3, 2016 at 2:06:12 PM UTC-4, Pete Griffin wrote: > > I was surprised to see all 4 cores (8 threads) being used in step-8 which > does not have PETSc/MPI support. In the solver, the main thread was using > 100% of it's resources. The others were using very consistently 24-25% > independent of #DOF. Is the normal SolverCG<> of step-8 multi-theaded? > Would the overall performance on a single processor improve if one were > able to have multiple controlling threads instead of one. Is it even > possible? This might be even more important for the 8 or 16 core CPUs I see > available now. If I am correct the code that exists was probably optimum > with Single or Dual Core CPUs but it does not appear to be true now. It may > not be feasible but I though I'd mention it. > > Also, it appears that the efficiency with one CPU decreases as the #DOF > increase with PETSc/MPI. Does anyone know why? > > Some parts of deal.II (including the solvers but not the preconditioners which may be what you are seeing here) are multithreaded. By default deal.II will use as many threads as possible. I am not sure what you mean by controlling threads but I have used multithreading on workstations with 64 cores and it works like expected. Since you have done zero effort to use multithreading in your code, you cannot expect to get 100% of usage on all your threads. This is also true if you use MPI. Deal.II will launch one process but it will use 8 threads.
Best, Bruo -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
